Four vehicles suffered damage when an axle broke off from a haulage lorry that was travelling along the A41 this morning.
It happened at around 11am just past the northbound Chesham junction.
Damage was caused to three cars and a small van and one of the vehicles suffered an oil leak.
One of the drivers, 19-year-old Tiffany Choules, said: “I just saw cars swerving in front of me and then all of a sudden this metal piping came out from under the car in front.
“It was too quick and I couldn’t avoid it. I hit it with my tyre and it immediately went as flat as a pancake. Luckily I managed to pull over and call the RAC, who are coming to replace my tyre.
“It could have been so much worse, the pipes could have come through my windscreen.”
Police have closed one lane along the stretch of road and officers are still at the scene.